A method of efficient diffusion

Abstract

The invention discloses a high efficiency diffusion method. The high efficiency diffusion method comprises steps that: a silicon chip is placed in a diffusion furnace, a gas containing a phosphor source is injected into the diffusion furnace, and first diffusion for the silicon chip is carried out; square resistance of the silicon chip is detected, when the square resistance value is 4-8 ohms / square smaller than a preset value, under the temperature of 690-720 DEG C, second diffusion for the silicon chip is carried out; under the protection of the nitrogen, furnace outgoing operation of the silicon chip is carried out. By employing the high efficiency diffusion method, after diffusion, a surface of the silicon chip has low doped concentration, a surface recombination rate is small, and photoelectric conversion efficiency of a solar cell is substantially improved.

Description

technical field [0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for efficient diffusion. Background technique [0002] Since the quality of the P-N junction directly affects the quality of the solar cell, the manufacture of the P-N junction has always been the focus of research in the solar cell manufacturing process. In order to produce a high-quality P-N junction, researchers have tried to use a variety of methods, for example: the manufacture can adopt a variety of methods, such as alloy method, diffusion method, ion implantation method and epitaxial growth method and so on. The P-N junctions produced by different manufacturing processes can be adapted to different needs. Adopting the method of diffusion to make P-N junction is the most widely used at present, so it is also the hotspot of research. [0003] The quality of the diffusion process determines the uniformity of impurity distribution. When the concentra...

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Problems solved by technology

[0004] To reduce the surface doping concentration, the most commonly used method is to reduce the flux of the phosphorus source, but this method will make the phosphorus source not fully mixed in the diffusion gas, which will cause uneven internal resistance of the silicon wafer after diffusion; at the same time, due to the phosphorus The source content is small, so to a large extent, the concentration of the phosphorus source at the inlet and outlet of the diffusion furnace has a large difference in phosphorus source concentration. This concentration difference will cause a large difference in the square resistance between the diffusion silicon wafers, that is The uniformity of square resistance becomes worse

In addition, due to the low concentration of phosphorus source, it is necessary to increase the diffusion process time or increase the diffusion temperature under the premise of ensuring sufficient doping amount; and in the case of low phosphorus source, high temperature diffusion will further affect the square resistance. Uniformity

[0005] From the above analysis, it can be seen that although the current diffusion technology can obtain a silicon wafer with a predetermined square resistance value, the square resistance uniformity is poor, the surface doping concentration of the silicon wafer is high, and the photoelectric conversion efficiency of the solar cell is low.

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